If you didn't find anything running a Smart Scan, then you probably don't have any ad-ware. Still, you won't know for sure until you run a full scan. I've found things running Full Scan when Smart Scan showed nothing. Did you reset your Power Settings to Never and check to see which button your "Sleep" hotkey is bound to?
As far as PSUs go, they're pretty much universal. That's usually one area where you don't have to worry about company parts.
I hope you are able to find and correct the problem. E-Machine, huh?